For now it simply includes reading in the reflog as a list of
entries. This does mean that the drop/append functions don't need to be
wrapped, as we can use erlang's list handling.
It however also means that we cannot write this back out, as there is
currently no way to create an empty reflog that we can fill with our own
list.
This means we no longer accept any iolist in some of the functions,
but we might bring it back later.
There is also a new function, geef_ref:create_symbolic() to create
symbolic references, since we can no longer differentiate between a
name and an OID.
Refernces contain three pieces of data which we already keep in the
erlang record. Keep the repository it belongs to in the record as well
and remove resource in the NIF. This makes the code easier to reason
about, as we don't need to keep any reference counts or GC the C
struct.
This does mean we cannot re-use references across geef_repo restarts,
but that's probably a good thing.
This makes it useful for users of the bindings. The naming is the same
as the module to allow elixir to treat the records in much the same
way as its native module/record hybrid.
